Малеин ангидридінің өндірісі және химиялық қасиеттері

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| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 409750643
| Reference=
| Name = Maleic anhydride
| ImageFileL1 Ref =
| ImageFileL1 = Maleic anhydride (vertical). svg
| ImageSizeL1 = 80px
| ImageNameL1 = Maleic anhydride
| ImageFileR1 = Maleic anhydride 3d. png
| ImageSizeR1 = 150px
| ImageFile2 = Sample of Maleic anhydride. jpg
| PIN = Furan 2,5 dione
| OtherNames = Maleic anhydride
| ExploLimits = 1.4% 7.1%
| REL = TWA 1 mg/m3 (0.25 ppm)

Maleic anhydride is produced by vapor phase oxidation of n butane. The overall process converts the methyl groups to carboxylate and dehydrogenates the backbone. The selectivity of the process reflects the robustness of maleic anhydride, with its conjugated double bond system. Traditionally maleic anhydride was produced by the oxidation of benzene or other aromatic compounds. As of 2006, only a few smaller plants continue to use benzene. In both cases, benzene and butane are fed into a stream of hot air, and the mixture is passed through a catalyst bed at high temperature. The ratio of air to hydrocarbon is controlled to prevent the mixture from igniting. Vanadium pentoxide and molybdenum trioxide are the catalysts used for the benzene route, whereas vanadium phosphate is used for the butane route:

Parallels exist with the production of phthalic anhydride: While older methods use naphthalene, modern methods use o xylene as feedstock.

The chemistry of maleic anhydride is very rich, reflecting its ready availability and bifunctional reactivity. It hydrolyzes, producing maleic acid, cis HOOC–CH=CH–COOH. With alcohols, the half ester is generated, e. g., cis HOOC–CH=CH–COOCH3. Maleic anhydride is a classic substrate for Diels Alder reactions. It was used for work in 1928, on the reaction between maleic anhydride and 1,3 butadiene, for which Otto Paul Hermann Diels and Kurt Alder were awarded the Nobel Prize in 1950. It is through this reaction that maleic anhydride is converted to many pesticides and pharmaceuticals. Their 1928 patent also provided many other examples of reactions involving maleic anhydride, such as the reaction with cyclopentadiene to form nadic anhydride. Michael reaction of maleic anhydride with active methylene or methine compounds such as malonate or acetoacetate esters in the presence of sodium acetate catalyst. These intermediates were subsequently used for the generation of the Krebs cycle intermediates aconitic and isocitric acids. Maleic anhydride dimerizes in a photochemical reaction to form cyclobutane tetracarboxylic dianhydride (CBTA). This compound is used in the production of polyimides and as an alignment film for liquid crystal displays. It is also a ligand for low valent metal complexes, examples being Pt(PPh3)2(MA) and Fe(CO)4(MA). On account of its cycle of 4 π electrons in an array of 5 atoms with p orbitals, maleic anhydride was long thought to exhibit antiaromaticity. However, a thermochemical study concluded that only 8 kJ/mol of destabilization energy can be ascribed to this effect, making it weakly antiaromatic at best.

Maleic anhydride has many applications.

Liquid maleic anhydride is available in road tankers and/or tank containers which are made of stainless steel, which are insulated and provided with heating systems to maintain the temperature of 65 75 °C. Tank cars must be approved for the transport of molten maleic anhydride. Liquid/molten maleic anhydride is a dangerous material in accordance with RID/ADR. Solid maleic anhydride pellets are transported by trucks. Packaging is generally in 25 kg polyethylene bags.

This compound poses relatively low risk environmental hazards, an important feature for some applications. In humans, exposure to maleic anhydride may cause irritation to the respiratory tract, eyes, exposed mucosa, and skin. Maleic anhydride is also a skin and respiratory sensitizer. Maleic anhydride is a low hazard profile chemical. Maleic anhydride rapidly hydrolyzes to form maleic acid in the presence of water and hence environmental exposures to maleic anhydride itself are unlikely. Maleic acid is biodegradable under aerobic conditions in sewage sludge as well as in soil and water. Food starch for use in night markets sold from a supplier in Tainan city, Taiwan, were found to contain maleic anhydride in December 2013. The supplier was investigated regarding the 300 tons of tainted starch; an earlier inspection in November had found 32 tons.